Hypermedia Glossary Of Genetic Terms
|CpG island||Short region of DNA in which the frequency of the CG sequence is higher than in other regions. "p" indicates that "C" and "G" are connected by a phosphodiester bond.
CpG islands are often located around the promoters of housekeeping genes (which are essential for general cell functions) or other genes frequently expressed in a cell.
|Deoxyribonucleic acid (DNA)||The molecule that encodes genetic information. DNA is a double-stranded molecule held together by weak bonds between base pairs of nucleotides. The four nucleotides in DNA contain the bases: adenine (A), guanine (G), cytosine (C), and thymine (T). In nature, base pairs form only between A and T and between G and C; thus the base sequence of each single strand can be deduced from that of its partner.|
|Base sequence||The order of nucleotide bases in a DNA molecule. Length is usually defined as the number of base pairs. Cf. sequence, DNA sequence.|
|Cytosine (C)||Cytosine is a pyrimidne base (nitrogenous base) and constituent of nulceotides and as such one member of the base pair G-C (guanine and cytosine) .
|Guanine (G)||Guanine is a purine base (nitrogenous base) and constituent of nucleotides and as such one member of the base pair G-C (guanine and cytosine).
|Promoter||The term introduced by Jacob, Ullman and Monod (1964) for a site on DNA that is upstream (5') to coding sequences (cf. operon) to which RNA polymerase will bind and initiate transcription.|
|Gene family||Groups of closely related genes that make similar products.|
|Gene expression||The process by which a gene's coded information is converted into the structures present and operating in the cell. Expressed genes include those that are transcribed into mRNA and then translated into protein and those that are transcribed into RNA but not translated into protein (e.g., transfer and ribosomal RNAs).
The degree of expression is called expressivity.
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